/*
 * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.javac.model;

import static com.sun.tools.javac.code.Flags.SYNTHETIC;

import java.util.AbstractList;
import java.util.Iterator;
import java.util.NoSuchElementException;

import com.sun.tools.javac.code.Scope;
import com.sun.tools.javac.code.Symbol;

/**
 * Utility to construct a view of a symbol's members, filtering out unwanted
 * elements such as synthetic ones. This view is most efficiently accessed
 * through its iterator() method.
 * 
 * <p>
 * <b>This is NOT part of any supported API. you write code that depends on
 * this, you do so at your own risk. This code and its internal interfaces are
 * subject to change or deletion without notice.</b>
 */
public class FilteredMemberList extends AbstractList<Symbol> {

	private final Scope scope;

	public FilteredMemberList(Scope scope) {
		this.scope = scope;
	}

	public int size() {
		int cnt = 0;
		for (Scope.Entry e = scope.elems; e != null; e = e.sibling) {
			if (!unwanted(e.sym))
				cnt++;
		}
		return cnt;
	}

	public Symbol get(int index) {
		for (Scope.Entry e = scope.elems; e != null; e = e.sibling) {
			if (!unwanted(e.sym) && (index-- == 0))
				return e.sym;
		}
		throw new IndexOutOfBoundsException();
	}

	// A more efficient implementation than AbstractList's.
	public Iterator<Symbol> iterator() {
		return new Iterator<Symbol>() {

			/** The next entry to examine, or null if none. */
			private Scope.Entry nextEntry = scope.elems;

			private boolean hasNextForSure = false;

			public boolean hasNext() {
				if (hasNextForSure) {
					return true;
				}
				while (nextEntry != null && unwanted(nextEntry.sym)) {
					nextEntry = nextEntry.sibling;
				}
				hasNextForSure = (nextEntry != null);
				return hasNextForSure;
			}

			public Symbol next() {
				if (hasNext()) {
					Symbol result = nextEntry.sym;
					nextEntry = nextEntry.sibling;
					hasNextForSure = false;
					return result;
				} else {
					throw new NoSuchElementException();
				}
			}

			public void remove() {
				throw new UnsupportedOperationException();
			}
		};
	}

	/**
	 * Tests whether this is a symbol that should never be seen by clients, such
	 * as a synthetic class. Returns true for null.
	 */
	private static boolean unwanted(Symbol s) {
		return s == null || (s.flags() & SYNTHETIC) != 0;
	}
}
